ROCK & GEM FIELD GUIDE..
BY RICHARD GROSS & PAM FREEMAN
Oco Geodes
In a remote area known as Tres Pinheiros (Three Pines) near the southern border of Brazil at an elevation of 3,000 feet, one finds unusual geodes known as Oco or Ocho geodes. This area’s geological history, characterized by volcanic activity and lava flows, provides the perfect conditions for the formation of these tiny geodes.